1. Field of the Invention
The present invention generally relates to a fuse box of a semiconductor device. More specifically, the present invention provides a device of forming a uniformly residual oxide film by rearranging fuse boxes in consideration of an etching ratio depending on plasma density of the semiconductor device to prevent a fuse attack.
2. Description of the Related Art
When one of fine cells has a defect, a semiconductor device such as a DRAM or a SRAM is not properly operated so that it is regarded as defective. However, although it is possible to generate defects in a small number of cells due to increase in the integration degree of a semiconductor memory device, it is ineffective to destroy the semiconductor memory devices having defects to reduce yield.
When a defect is generated in a cell of a specific region during a manufacturing process of a semiconductor memory device, a new column or row line has been substituted for a column or row line where a cell having a defect is located.
A metal fuse is used to disconnect a specific device electrically when a defective element is generated in a circuit structure of the semiconductor device. That is, a repair process is performed to prevent the whole memory device from being discarded when a fail is generated in a part of the fuse. In the repair process, a laser cutting is performed in the fuse having the fail to disconnect the fuse having the fail. A fuse is called a wire cut by radiation of laser, and a fuse box is called this cut region and its enclosed region.
The fuse box includes a redundancy fuse box to control cell redundancy, and an option fuse box comprising an option fuse to control an option circuit for evaluating product property or a level of an internal voltage.
However, the conventional redundancy fuse box has a large open region because the number of fuses is large to control redundancy fuses. Relatively, the option fuse box has a smaller open region because there are a few numbers of fuses corresponding to each function.
Hereinafter, a large fuse box refers to a fuse box having a large open region of the fuse box such as the redundancy fuse box, and a small fuse box refers to a fuse box having a small open region of the fuse box such as the option fuse box.
FIGS. 1 and 2 are plane diagrams illustrating a conventional fuse box of a semiconductor device.
The conventional fuse box comprises four banks 3 in a die 1. A large fuse box 4 having a large open region is formed in a peripheral circuit region 2 between bank 3 regions. A small fuse box 5 having a small open region is formed which is separated at a long distance from the large fuse box 4.
FIG. 2 is a diagram illustrating a residual oxide film 6 formed on a fuse f1 of the large fuse box 4 and a residual oxide film 7 formed on a fuse f2 of the small fuse box 5. While a large number of the residual oxide films 6 remains on the fuse f1 when the large fuse box 4 is taken along the line A-A′, a few number of the residual oxide films 7 remains on the fuse f2 when the small fuse box 5 is taken along the line A-A′.
A repair etching process which is an open process of the fuse box is to perform a dry etching process by plasma. Here, a loading effect phenomenon occurs which represents a difference of an etching ratio of the oxide film depending on a difference of pattern density. Due to the loading effect phenomenon, the residual oxide film of the fuse f1 of the large fuse box 4 remains to have a thicker thickness than that of the fuse f2 of the small fuse box 5.
As a result, it is important to effectively control the residual oxide film formed on the repair fuse in the fuse box in a DRAM chip in order to secure stability of a blowing process of the fuse.
The residual oxide film formed on the fuse remains to have a predetermined thickness which satisfies the optimum fuse blowing condition. However, when there is a difference between the residual oxide films 6 and 7 depending on the loading effect phenomenon of the large fuse box 4 and the small fuse box 5, it is difficult to set an optimum target of the residual oxide film on the fuse.
When the repair etching process is performed at a target of the residual oxide film adjusted to a redundancy fuse box so as to secure stability of FTA (Fixed To Attempt) yield which represent a repair success rate of a redundancy cell, there is no residual oxide films on the fuse by the loading effect in the repair etching process. As a result, a fuse attack occurs to cause malfunction of an option circuit or generate a fail in the DRAM operation by an abnormal shift of an internal voltage.
The smaller number of the residual oxide films 6 and 7 of fuse lines formed on the edge of the same fuse box remains than that of the residual oxide films 6 and 7 of the fuse line formed on the inner side of the same fuse box to degrade a fuse blowing success rate of the outer fuse lines.
To increase the success rate, a dummy fuse line is added on the outside of the outer fuse lie. In other words, the same number of dummy fuse lines, for example two dummy fuse lines, are formed at both ends of the fuse boxes 4 and 5. The conventional fuse box comprises 4 dummy fuse lines in the large fuse box 4 and other 4 dummy fuse lines in the small fuse box 5.
However, the addition of dummy fuse lines increases the layout area to increase the size of the die and reduce the number of net dies produced in a wafer.